Process for curing polyepoxides and resulting products



3,297,635 PROCESS FOR CURING POLYEPOXIDES AND RESULTING PRODUCTS ElliotBergman and William De Acefis, Berkeley, Calif., assignors to Shell OilCompany, New York, N.Y., a

corporation of Delaware No Drawing. Filed May 31, 1963, Ser. No. 284,36514 Claims. (Cl. 260 -47) group, and preferably in addition anaccelerating material such as a tertiary amine. The invention furtherprovides cured products obtained by the above-described process.

Polyepoxides, such as, for example, those obtained by reactingepichlorohydrin with polyhydric phenols in the presence of caustic, arepromising materials for use in United States Patent many industrialapplications as they can be reacted with I curing agents to forminsoluble infusible products having good chemical resistance. Theconventional polyepoxidecuring agent systems, however, have certaindrawbacks that have limited their use for certain applications. example,the known systems take considerable time to cure at low temperatures.With the best aliphatic type amine curing agents, the systems takeseveral hours to set to a hard product. Because of this, it has beendiflicult to use the polyepoxide systems for applications, such ashighway coatings, maintenance surface coatings and the like, where thecoating must dry in a very short time.

It has been found that certain types of polymercaptans can be used tocure the polyepoxides at a rapid rate at the low temperatures. The useof these materials, how- V ever, has been limited because they have astrong odor, in some cases are toxic, and in most cases are very thickliquids or solids which are difficult to mix with the polyepoxides.Furthermore, the properties of the cured products are not as good asdesired for certain applications.

It is an object of the invention, therefore, to provide a new processfor curing polyepoxides. It is a further object to provide a new processfor curing polyepoxides at a fast rate at low temperatures. It is afurther object to provide a process for curing polyepoxides to a hardproduct in a matter of minutes. It it a further object to provide aprocess for curing polyepoxides at a fast rate to form products havinggood strength and resistance to water, solvents and alkali. It is afurther object to provide new low temperature curing agents forpolyepoxides which have little or no odor. It is a further object toprovide new curing agents for polyepoxides which are substantiallynon-toxic. It is a further object to provide new class of polymercaptansthat can be used to cure polyepoxides at low temperatures. These andother objects of the invention will be apparent from the following3,297,635 Patented Jan. 10, 1967 amine, cure the polyepoxide in a matterof minutes to form a hard coating. Furthermore, the cured product hasexcellent hardness and strength and good resistance to water, solventsand alkali. Of particular importance is the fact that these specialmercaptans have little, if any, odor, are substantially non-toxic andare generally liquids which can be easily mixed into the polyepoxidecompositions without the .use of solvents or diluents.

The new curing agents to be used in the process of the inventioncomprise the cyclic, and preferably heterocyclic, compounds which aresubstituted on at least three different elements in the ring with aradical containing a mercapto group. The compounds are preferablymononuclear but may contain two or more ring structures which may beseparate or joined together. The mercapto groups are preferably not morethan 6 carbon atoms removed from the ring. In addition, the rings arepreferably 5 to 7 membered rings and preferably contain in addition tocarbon a heteroatorn, such as oxygen, sulfur, nitrogen, phosphorous andthe like.

Examples of these compounds include, among others the tn'oXanes,trithianes, dioxathianes, oxadithianes, oxazines, triazines, thiazines,dithiazines, dioxarsenoles, oxathiazoles, dithiaz-oles, triazoles,dioxalanes, isoxazoles, isothiazoles, dioxaborines, dioxazines,thiadiazines, and the like, which have at least threemercapto-substituted radicals attached to the said rings.

' Specific examples of these include, among others,

2,4,6-tris(beta-mercaptoethyl) 1,3,5-tn'oxane2,4,6-tris(beta-mercaptoethyl) 1,3,5-trithiane2,4,6-tris(mercaptomethyl) 1,3,5-trioxane 2,4,6-tris(mercaptomethyl)1,3,5-trithiane 2,4,6-tris(beta-mercaptoethyl) 1,3-dioxa-5-thiane2,4,6-tris(beta-mercaptoethyl) 1oxa-3,5-dithiane2,4,5-tris(beta-mercaptoethyl) 1,3-dioxalane 2,4,5-tris (mercaptomethyl)1,3-dioxalane 2,4,6-tris(alpha-methyl-beta-mercaptoethyl) 1,3,5-trioxane2,4,6-tris(beta-methyl-beta-mercaptoethyl) 1,3,5-trithiane 2,4,6tris(beta-mercaptobutyl) 1,3,5-trioxane 2,4,6-tris(beta-mercaptohexyl)1,3,5-trithiane 2,4,6-tris (beta-phenyl-beta-mercaptoethyl)1,3,5-trioxane 2,4,6-tris(beta cyclohexyl beta mercaptoethyl) 1,3,5-

trioxane 2,4,6-trimercapto 1,3,5-trioxane 2,4,6-trimercapto1,3,5-trithiane 2,4,6-tris(1-thia-4-mercaptobutyl) 1,3,5-tn'oxane2,4,6-tris(1-oxa-4-mercaptobutyl) 1,3,S-trioxane 2,3,6-tris(beta-mercaptoethyl) 1,4-ox-azine 2,4,6-tris 3-mercaptopropyl) 1,3,5-triazine 2,4,6-tris(mercaptomethyl) 1,3,5-triazine2,4,6-t-ris(beta-mercaptoethyl) l-thia-3,5-diazine and O-CHO HSGHzCHz-CCH-CHz-CHz-SH OCH-O ICH2CH2SH OH2CH2SH I HS-CHzCH CHzCHzSH HaSH Alsoincluded in the above are the polymeric polymercaptans as obtained byjoining two or more of the above compounds together as or by couplingreactions with dialdehydes and the like.

Preferred members of the above group comprise the heterocyclicpolymercaptans of the general formula 1 +01 s11). X X

wherein at least one X is a member of the group consisting of oxygen,sulfur and nitrogen, and the remaining Xs are carbon atoms which whennot attached to the mercaptan containing radical are attached in theremaining valences to members of the group consisting of hydrogen,halogen and alkyl radicals, and R is a bivalent hydrocarbon radical andn is an integer of 3 to 5.

Particularly preferred polymercaptans are those of the formula wherein Zis a member of the group consisting of oxygen, sulfur and nitrogen and Ris a bivalent hydrocarbon radical, preferably containing from 1 to 6carbon atoms.

Of special interest are the poly(mercaptoalkyl) trioxanes,poly(m'ercaptoalkyl) trithianes, the poly(mercap toalkyl) triazines, andcombinations thereof, such as the poly(mercaptoalkyl) thiadioxanes,wherein the alkyl groups contain from 1 to carbon atoms.

Of particular interest are the cycloaliphatic acting (i.e., nonaromatic)heterocyclic oxygen containing and sulfur containing products andespecially those derived by trimerization, cot-rimerization,tetramerization, coand tritetramerization of chlorinated aldehydes andthen converting to the meracpto derivative as noted below.

The polymercaptans of the present invention can be prepared by a varietyof methods. They may be prepared, for example, by reacting thecorresponding chloride compound with an alkali metal salt of athioalkanoic acid, such as sodium thioacetic acid and then refluxing theresulting thioester with methanol or ammnoia to form the mercaptanproduct. This reaction may be illustrated by the following equationshowing the preparation of 2,4,6-

o on oosN.

o ,J olonion \O oniornoi CH=CN ll CHIzCHzS-C CH; C

The starting material in the above reaction are those compounds asdescribed above wherein a halogen replaces the mercapto group. Thepreferred halogenated compounds of this type are preferably obtained bythe trimerization, tetramerization of halogenated aldehydes, such aschloropropionaldehyde chlora'cetaldehyde, dichloropropionaldehyde andthe like. In making these, one may use the same or mixture of aldehydes,or mixtures with non-halogen containing aldehydes.

The alkali metal salt of a thioalkanoic acid employed in the reaction ispreferably a sodium salt, such as sodium t'hioacetate. This salt isemployed in at least one molar amount for every halogen atom to beconverted, and preferably in an excess, such as up to 30 or 40% excessof the theoretical amount.

The reaction may be accomplished with or without solvents or diluents,but it is generally preferred to utilize solvents, 'such asacetonitrile, tetrahydrofuran, dimethyl formamide, dimethyl sulfoxide,methanol and the like.

The reaction with the alkali metal salt is preferably accomplished byapplying heat, with preferred temperatures varying from about 50 C. toC. In general, it is preferred to conduct the reaction at refluxtemperature.

The resulting thioesters may be recovered as such before conversion tothe mercaptan derivative or they may be further treated withoutrecovery, The thioesters may be recovered by filtration to remove thesalt formed in the reaction, and then extracted or stripped to removethe solvents or diluents employed in the reaction mixture. Whenrecovered, the thioesters appear as fluid liquids to crystalline solids.They possess at least three thioester groups, i.e.,

groups and can be utilized in various applications, such asplasticizers, etc., in addition to their use as intermediates for thepreparation of the polymercaptans.

The thioester can be converted to the mercaptan by any suitable method.One method comprises reacting the thioester with alcohol or withammonia. The preferred method comprises reacting the thioester with atleast an equivalent amount of alcohol, such as methanol, i.e., at leastone mole of alcohol per thioester group to be .converted. This reactionis preferably accomplished by application of heat, e.g., temperaturesranging from about 50 C. to 100 C., and still more preferably at thereflux temperature. If ammonia is employed, it is preferably bubbledinto an alcohol solution of the thioester and the mixture allowed tostand at room temperature for several hours.

The desired polymercaptan can be recovered from the reaction mixture byany suitable method, such as extraction, distillation and the like. Itis generally preferred to strip out the solvent and then distill toobtain the pure heterocyclic polymercaptan.

The new polymercaptans can also be prepared by other suitable methods.One additional method comprises reacting the correspondinghalogen-substituted heterocyclic compound with sodium bisulfide underhydrogen sulfide pressure. The sodium bisulfide is preferably employedin excess of that needed to convert the halogen atoms, and is preferablyused in amounts varying from about 2 to 5 times the amount needed forconversion. The reaction with sodium bisulfide is preferablyaccomplished in the presence of a solvent or diluent, such as ethanol,methanol or mixtures of alcohols with water. The temperature employedfor the reaction will preferably vary from about 50 C. to 120 C. with apreferred range varying from about 70 to 80 C. The pressure of thehydrogen sulfide preferably varies from about 200 to 600 p.s.i.g. Inrecovering the desired product, the hydrogen sulfide pressure isreleased, the product neutralized with acetic acid and the mixturestripped of solvent and subsequently distilled to give the desiredheterocyclic polymercaptan.

Another less preferred method comprises reacting the halogenatedderivative with thiourea in a solvent, such as ethanol, and thenreacting the resulting product with ammonia to convert the thiouroniumsalt to the desired polymercaptan. The conversion may also beaccomplished by a special technique of reacting the thiouronium saltwith sodium bisulfide.

The new heterocyclic polymercaptans of the present invention are fluidto viscous liquids or solids. They have active mercapto groups and 'atleast three per molecule. They are generally free of odor and non-toxic.They are soluble in conventional solvents, such as benzene, aliphatichydrocarbons, ethers, esters and the like. They are also compatible withconventional resins, tars, oils, polymers and the like, such asasphalts, coal tars, rosin, phenolformaldehyde resins, vinyl polymers,and particularly epoxy resins.

As noted above, they are particularly useful and valuable as curingagents for the polyepoxides.

The polyepoxides to be used in the process of the invention comprisethose materials possessing more than one vicinal epoxy group, i.e., morethan one group. These compounds may be saturated or unsaturated,aliphatic, cycloaliphatic, aromatic or heterocyclic and may besubstituted with substituents, such as chlorine, hydroxyl groups, etherradicals and the like. They may be monomeric or polymeric.

For clarity, many of the polyepoxides and particularly those of thepolymeric type are described in terms of epoxy equivalent values. Themeaning of this expression is described in U.S. 2,633,458. Thepolyepoxides used in the present process are those having an epoxyequivalency greater than 1.0.

Various examples of polyepoxides that may be used in the process of theinvention are given in U.S. 2,633,458 and it is to be understood that somuch of the disclosure of that patent relative to examples ofpolyepoxides is incorporated by reference to this specification.

Other examples include the epoxidized esters of the polyethylenicallyunsaturated monocarboxylic acids, such as epoxidized linseed, soybean,perilla, oiticia, tung, walnut and dehydrated castor oil, methyllinoleate, butyl linoleate, ethyl 9,12-octadecadienoate, butyl9,12,15-octadecatrienoate, butyl eleostearate, monoglycerides of tungoil fatty acids, monoglycerides of soybean oil, sunflower, rapeseed,hempseed, sardine, cottonseed oil and the like. Another group of theepoxy-containing materials used in the process of the invention includethe epoxidized esters of unsaturated monohydric alcohols andpolycarboxylic acids, such as, for example, di(2,3-epoxybutyl) adipate,di(2,3-epoxybutyl) oxalate, di(2,3-epoxyhexyl) succinate,di(3,4-epoxybutyl) maleate, di(2,3-epoxyoctyl) pimelate,di(2,3-epoxybutyl) pht-halate, di(2,3-epoxyoctyl) tetrahydrophthalate,di(4,5-lepoxydodecyl) maleate, di-

(2,3-epoxybutyl) terephthalate, di(2,3-epoxypentyl) thio-' dipropionate,di(5,6-epoxytetradecyl) diphenyldicarboxylate, di(3,4-epoxyheptyl)sulfonyldibutyrate, tri(2,3-epoxybutyl) l,2,4-butanetricarboxylate,di(5,6-epoxypentadecyl) tartarate, di(4,5-epoxytetradecyl) maleate,di(2,3- epoxybutyl) azelate, di(3,4-epoxybutyl) citrate, di(5,6-epoxyoctyl) cyclohexane-1,2-dicarboxylate, di(4,5-epoxyoctadecyl)malonate.

Another group of the epoxy-containing materials includes thoseepoxidized esters of unsaturated alcohols and unsaturated carboxylicacids, such as 2,3epoxybutyl 3,4- epoxypentanoate, 3,4-epoxy hexyl3,4-epoxyhexyl 3,4- epoxypentanoa-te, 3,4 epoxycyclohexyl 3,4epoxycyclohexanoate, 3,4-epoxycyclo'hexyl 4,5-epoxyoctanoate, 2,3-epoxycyclohexylmethyl epoxycyclohexane carboxylate.

Still another group of the epoxy-containing materials includedepoxidized derivatives of polyethylenically unsaturated polycarboxylicacids such as, for example, dimethyl 8,9,12,13-diepoxyeicosanedioate,dibutyl 7,8,11,12 diepoxyoctadecanedioate, dioctyl10,l1-diethyl-8,9,12,l3- diepoxy-eiconsanedioate, dihexyl6,7,10,1l-diepoxyhexadecanedioate, didecyl9-epoxy-ethyl-10,1l-epoxyoctadecanedioate, dibutyl 3-butyl 3,4,5,6diepoxycyclohexane- 1,2 dicarboxylate, dicyclohexyl 3,4,5,6diepoxycyclohexane-1,2-dicarboxylate, dibenzyll,2,4,5-diepoxycyclohexane-1,2-dicarboxylate and diethyl5,6,10,11-diepoxyoctadecyl succinate.

Still another group comprises the epoxidized polyesters obtained byreacting an unsaturated polyhydric alcohol and/or unsaturatedpolycarboxylic acid or anhydride groups, such as, for example, thepolyester obtained by reacting 8,9,12,l3-eicosanedienedioic acid withethylene glycol, the polyester obtained by reacting diethylene glycolwith 2-cyclohexene-1,4-dicarboxylic acid and the like, and mixturesthereof.

Still another group comprises the epoxidized .polyethylenicallyunsaturated hydrocarbons, such as epoxidized 2,2-bis(2-cyclohexenyl)propane, epoxidized vinyl cyclohexene and epoxidized dimer ofcyclopentadiene.

Another group comprises the epoxidized polymers and copolymers ofdiolefins, such as butadiene. Examples of this include, among others,butadiene-acryonitrile copolymers (Hycar rubbers), butadiene-styrenecopolymers and the like.

Another group comprises the glycidyl containing nitrogen compounds, suchas diglycidyl aniline and diand triglycidylaminel The polyepoxides thatare particularly preferred for use in the compositions of the inventionare the glycidyl ethers and particularly the glycidyl ethers ofpolyhydric phenols and polyhydric alcohols. The glycidyl ethers ofpolyhydric phenols are obtained by reacting epichlorohydrin with thedesired polyhydric phenolsin the presence of alkali. Polyether A andPolyether B described in the above-noted U.S. 2,633,458 are goodexamples of polyepoxides of this type. Other examples include thepolyglycidyl ether of 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane (epoxy'value of 0.45 eq./-100 g. and melting point C.), polyglycidyl ether of1,1,5,5-tetrakis (hydroxyphenyl) pentane (epoxy value of 0.514 eq./.100g.) and the like and mixtures thereof.

The amount of new polymercaptans to be employed in the cure of thepolyepoxide may vary within certain limits. -In general, thepolyepoxides are combined with at least .8 equivalent of thepolymercaptan. As used sulfate,

arsines, organic antimony compounds, amines, amine salts or quaternaryammonium salts, etc. Preferred activators are the phenols, phosphines,arsines, amines, and sulfides, such as, for example benzyldimethylaminedicyandiatmide,

'p,p-bis(dimethylaminophenyl) methane, pyridine, di-

methyl aniline, dimethylethanolamine, methyldiethanolamine, morpholine,dimethylaminopropylamine, dibutyl aminopropylamine,stearyldimethylamine, tri n butyl amine, N,N-dibutyl butylamine,tri-n-hexylamine, ethyl I di-n-propylamine, phenylene diamine,diethylene triamine,

dibutyl sulfide, dioctyl sulfide, dicyclohexyl sulfide and the like, andmixtures thereof. The salts may be exemplified 4 by the inorganic andorganic acid salts of the amines, such as, for example, thehydrochloride, sulfate and acetate of each of the above-describedtertiary amines. The quaternary ammonium salts may be exemplified by thefollowing: benzyltrimethylammoni-um chloride, phenyltributylammoniumchloride, cyclohexyltributylammonium benzyltrimethylammonium sulfate,benzyltrimethylammoninm borate, diphenyldioctylammonium chloride, andthe like, and mixtures thereof.

Preferred activators to be used are the sulfides, phosphines andtertiary amines, and more preferably the monoand diamines wherein theamine hydrogens have been replaced by aliphatic, cycloaliphatic oraromatic hydrocarhon radicals containing not more than carbon atoms,

such as, for example, the trialkyl amines, triaryl amines,

triarylalkylamines, alkyl arylalkyla-mines, tricycloalkylamines, alkyldicycloalkylamines, diaminoalkanes, diakylene triamines, phenylenediamines and di(aminoaryl) alkanes. Preferred amine salts are thehydrochloride, sulfate and acetate of the above-described preferredamines. The preferred quaternary salts are those of the formula Y X R \Rwherein Y is nitrogen, R is an alkyl, aryl or arylalkyl radical,preferably containing no more than 12 carbon atoms and X is chlorine.

The activators noted above are generally employed in amounts varyingfrom 0.1 part of 4 parts per 100 parts of polyepoxide, and preferablyfrom 1 part to 3 parts per 100 parts of polyepoxide.

In curing the polyepoxides, it is usually desirable to have thepolyepoxide in a mobile condition when the polymercaptan is added inorder to facilitate mixing. The polyepoxides, such as the glycidylpolyether of polyhydric phenols, are generally very viscous to solidmaterials at ordinary temperature. Wit-h those that are liquid, but tooviscous for ready mixing, they are either heated to reduce theviscosity, or have a liquid solvent added thereto in order to providefluidity. Normally solid members are likewise either melted or mixedwith a liquid solvent. Various solvents are suitable for achievingfluidity of the polyepoxide. These may be volatile solvents which escapefrom the polyepoxid-e compositions containing the adduct by evaporationbefore or during the curing such as, esters such as ethyl acetate, butylacetate, Cel'losolve acetate (ethylene glycol monoacetate), methylCel-losolve acetate (aoetate ethylene 'glycol monomethyl ether), etc.,ether alcohols, such as methyl, ethyl or butyl ether of ethylene glycolor diethylene glycol; chlorinated hydrocarbons such as trichloropropane,

chloroform, etc. To save expense, these active solvents may be used inadmixture with aromatic hydrocarbons such as benzene, toluene, xylene,etc., and/or alcohols such as ethyl, isopropyl or n-butyl alcohol.Solvents which remain in the cured compositions may also be used, suchas diet-hyl pht-halate, dibutyl phthalate and the like, as well ascyano-substituted hydrocarbons, such as acetonitrile, propionitrile,adiponitrile, benzonitrile, and the like. It is also convenient toemploy a :polyepoxide, such as one of the glycidyl polyethers of thedihydric phenol, in admixture with a normally liquid glycidyl polyetherof a poly-hydric alcohol. In fact, two or more of any of thepolyepoxides may be used together as mixtures. In such a case, theamount of the adduct added and commingled is based on the averageepoxide equivalent weight of the polyepoxide mixture.

Various other ingredients may be mixed with the polyepoxide subjected tocure with the novel addncts including pigments, filler, dyes,plasticizers, resins and the like.

The polyepoxides may be cured with the new polymercaptans by merelymixing the two components together, preferably in the presence of theabove-noted activators. The cure time may vary from a few minutes to afew hours depending on the type and quantity of reactants and presenceof catalyst. Generally, in the presence of activators, the cure takesplace readily at room temperature. Fast reaction may be obtained, ofcourse, by applying heat. Preferred temperatures range from about 20 C.to 200 C. With small castings, it is preferred to cure at roomtemperature and then post cure for a few hours at elevated temperatures,say 40 C. to 170 C.

One important application of the use of the new polymercaptans as curingagents for polyepoxides is in the preparation of laminates or resinousparticles reinforced with fibrous textiles. Although it is generallypreferred to utilize glass cloth for this purpose, any of the othersuitable fibrous materials in sheet form may be employed such as glassmatting, paper, asbestos paper, mica flakes, cotton batts, duck, muslin,canvas and the like. It is useful to prepare the laminates from wovenglass cloth that has been given prior treatment with well knownfinishing or sizing agents therefor, such as chrome methacrylate orvinyl trichlorosilane.

In preparing the laminate, the sheets of fibrous materials arepreferably first impregnated with the mixture of the .polyepoxide,poly-mercaptan and activator. This is conveniently accomplished bydissolving the polymercaptan in a solvent and mixing the solution withthe polyepoxide so as to obtain a fluid mixture. The sheets of fibrousmaterial are impregnated with the mixture by spreading it thereon or bydipping or otherwise immersing them in the impregnant. The solvent isconveniently removed by evaporation and the mixture is cured by theapplication of heat. A plurality of the impregnated sheets can besuperimposed and the assembly cured in a heated press under a pressureof about 25 to 500 or more pounds per square inch. The resultinglaminate is extremely strong and resistant against the action of organicand corrosive solvents.

The new compositions of the invention are particularly outstanding asadhesives. In this application they can be used as a paste or solutiondepending on the method of preparation as described above. Othermaterials may also be included in the composition, such as pigments,plasticizers, stabilizers and reinforcing fillers, such as aluminumpowder, asbestos, powdered mica, zinc duct,

entonite, ground glass fibers, Monetta clay and the like. These fillersare preferably used in amounts varying from about 10 parts to 200 partsper parts of the polyepoxide and polymercapta-n compound. Othermaterials that may be included include other types of resins, such asphenol-aldehyde resins, urea-aldehyde resins, furfural resins,polyacetal resins, carbonate resins, polyamide resins, and the like.

The films had excellent gloss and appearance and good adhesion to thetin plates. The properties of the resulting coating are as follows:

Set to touch, min 20. Cotton free, min. 30. Dry hand, min 40. mandrelflex test Passed. Pencil hardness HB. Solvent, 15 min:

Toluene Unchanged. Methyl isobutylketone Unchanged. Cold water, 24 hoursUnchanged. aqueous NaOH, 60 min Unchanged.

EXAMPLE VI This example illustrates the preparation and properties of2,4,6-tris(mercaptomethyl) 1,3,5-trioxane.

95.5 parts of 2,4,6-tris(chloromethyl) 1,3,5-trioxane prepared bytrimerization of chloroacetaldehyde was dissolved in 500 parts ofacetonitrile. This mixture along with 162 parts of sodium triolacetatewas charged to a reaction flask equipped with stirrer, thermometer andnitrogen inlet. The mixture was brought to reflux under nitrogen andagitated at that temperature for about 50 hours. The reaction mixturewas then added to an ethanol/Water mixture. The organic layer wasremoved and washed. The organic phase was then dried, filtered andstripped at 40 C. 2-3 mm. to yield a light tan liquid.

2,4,6-tris(beta-mercaptoethyl) 1,3,5-trithiane was prepared from thetrimer of chlorothiopropionaldehyde by the method shown in Example I.About 60 parts of this material was combined with 100 parts of PolyetherA and 2 parts of benzyldimethylamine and the mixture spread out as acoating and cured in air at 25 C. The film cured in a short time to forma hard tough resistant coating.

EXAMPLE VIII 2,4,6 tris(alpha,beta dimercaptoethyl) 1,3,5-trioxane wasprepared by reacting dichloropropionaldehyde trirner with sodiumthiolacetate and treating the resulting product with ammonia. About 50parts of this material was combined with 100 parts of Polyether A and 2parts of tributylamine and the mixture spread out as a coating and curedin air at 25 C. The film cured in a short time to form a hard toughresistant coating.

EXAMPLE IX 2,4,5-tris(beta-mercaptoethyl) 1,3-dioxalane is prepared byreacting 2,4,5-tris(beta-chloroethyl) 1,3-dioxalane with sodiumthiolacetate and treating the resulting product with ammonia. Aboutparts of this material is combined with 100 parts of Polyether A and 2parts of benzyldimethylamine and the mixture spread out as a coating andcured in air at 25 C. The film cured in a short time to form a hardtough resistant coating.

EXAMPLE X Examples I, H and III are repeated with the exception that thepolymercaptan employed is: 2,4,6-tri(beta-mercaptoethyl)l-oxa-3,5-dithiane, 2,4,6-tris(beta-mercaptobutyl) 1,3,5-trioxane,2,3,6-tris(beta-mercaptoethyl) 1,4- 5

oxazine and 2,4,6-tris(mercaptobutyl) 1,3,5-triazine. Related resultsare obtained.

EXAMPLE XI Examples I, VI, VII and VIII are repeated with the exceptionthat the polyepoxide employed is: Polyether B, Polyether C, diglycidylether of resorcinol, 1,3,5-triglycidylbenzene, diglycidyl ester ofphthalic acid, epoxidized cyclohexenylmethylcyclohexenylmethylcarboxylate, and epoxidized di-(cyclohexenyl) propane.Related results are obtained.

We claim as our invention:

1. A process for curing and resinifying a polyepoxide having more thanone Vic-epoxy group which comprises mixing and reacting the polyepoxidewith a heterocyclic compound substituted in from 3 to 5 dilferent placeson the heterocyclic ring with 2. SH radical or a -RSH radical wherein Ris an aliphatic hydrocarbon radical containing from 1 to 6 carbon atoms,the heteroatom in the heterocyclic ring being a member of the groupconsisting of oxygen, sulfur and nitrogen.

2. A process for curing and resinifying a polyepoxide having more thanone Vic-epoxy group which comprises mixing and reacting the polyepoxidewith a curing amount of a heterocyclic compound substituted in at leastthree different places on the heterocyclic ring with a SH group or RSI-Igroup wherein R is an aliphatic hydrocarbon radical containing 1 to 6carbon atoms, no two -SH or -RSH groups being attached to adjacentplaces on the ring and the heteroatom in the heterocyclic ring being amember of the group consisting of oxygen, sulfur and nitrogen, and inthe presence of an activator for the epoxymercaptan reaction.

3. A process as in claim 2 wherein the hetero atom in the heterocyclicring is oxygen.

4. A process as in claim 2 wherein the heterocyclic compound has thestructure:

wherein at least one X is a member of the group consisting of oxygen,sulfur, and nitrogen, and the remaining Xs are carbon atoms which whennot attached to the mercapto-substituted radical are attached in theremaining valences to members of the group consisting of hydrogen,halogen and alkyl radicals, R is an aliphatic hydrocarbon radicalcontaining from 1 to 6 carbon atoms and n is an integer from 3 to 5.

5. A process as in claim 2 wherein the heterocyclic compound is a tris(mercaptoalkyl) trioxane.

6. A process as in claim 2 wherein the heterocyclic compound is atris(mercaptoalkyl) trithiane.

7. A process as in claim 2 wherein the heterocyclic compound has thestructure wherein Y is a member of the group consisting of oxygen,sulfur and nitrogen and R is a bivalent aliphatic hydrocarbon radicalcontaining 1 to 6 carbon atoms.

8. A process as in claim 2 wherein the heterocyclic compound is2,4,6-tris(beta-mercaptoethyl) 1,3,5-trioxane.

9. A process as in claim 2 wherein the accelerator is a tertiary amine.

10. A process as in claim 2 wherein the polyepoxide is a glycidyl etherof a polyhydric compound of the group consisting of polyhydric phenolsand polyhydric alcohols.

The compositions may be used in the bonding of a great variety ofdifferent materials, such as metal-tometal to other materials, such asplastic, wood-to-wood, glass-to-glass, glass-to-metal, and the like.They are of particular value, however, in the bonding of the metal suchas aluminum-to-aluminum and steel-to-steel. When applied as an adhesive,the compositions .may simply be spread on the desired surface to formfilms of various thicknesses, e.g., 0.5 mil to 30 mils, and then theother surface superimposed and heat applied. Curing pressures can belight contact :pressures up to about 500 psi.

When the compositions are used as adhesives for metalto-metal bonding,it has sometimes been found advantageous to impregnate cotton, rayon,synthetic fiber or glass cloth textiles with the compositions, and thenuse the impregnated textiles as a bonding tape for joining the metals.Such tapes provide convenient means for handling and using thecompositions in adhesive applications. The tape is inserted between twometals desired to be joined, and the assembly is heated and baked tocure the resin whereby articles are obtained wherein the joined surfaceshave not only excellent strength at ordinary temperatures, but alsoretain good strength even though heated at quite elevated temperaturesfor long periods of time. A preferred tape for such use comprises aglass fiber textile impregnated or coated with a mixture of thepolyepoxide, phthalocyanine compound and atomized aluminum powder ordust.

To illustrate the manner in which the invention may be carried out thefollowing examples are given. It is to be understood, however, that theexamples are for the purpose of illustration and that the invention isnot to be regarded as limited to any of the specific conditions orreactants recited therein. Unless otherwise specified parts described inthe examples are parts by weight.

The :polyethers referred to herein by letter are those described in U.S.2,633,458.

EXAMPLE I This example .illustrates the preparation and properties of2,4,6-tris(betaamercaptoethyl) 1,3,5-trioxane and the intermediatetrithiolacetate derivative.

136.8 parts of beta-chloropropionaldehyde trimer, 193.1

were added to a reaction flask and refluxed for 3 /2 hours (.pot temp.87 C.) with agitation under nitrogen. The reaction mixture was thenfiltered to remove salts. The filtrate was stripped and stabilized at 40C./1 mm. The

- parts of sodium thiolacetate and 587.0 parts of acetonitrile.

product (93% yield) was a dark, viscous oil identified as thetri-thiolacetate derivative I ll CH2CH2S-C-CH3 Analysis.Percent C theory45.4, found 45.1; percent H theory 6.06, found 6.1; percent S theory24.3,

Analysis.Percent C theory 40.0%, found 41.0%; percent H theory 6.7%,found 6.7%; percent S theory 10 35.6%, found 34.0%; mercapta-n 0.98 eq./g., theory 1.11eq./100 g.

About 100 parts of Polyether D, 22 parts of 2,4,6-tris(beta-mercaptoethy-l) 1,3,5-trioxane produced above, 2 parts oftris(dimethylaminomethyl) phenol and 43 parts of 50/50 mixture tolueneand methyl ethyl ketone were mixed together with stirring. The resultingfluid composition was spread out as a coating (about 2.5 mils thick) ontin panels. The coating was allowed to cure in air at 25 C. Theproperties of the resulting coating are as follows:

Set to touch, min. 20. Cotton free, min. 30. Dry hand, min. 40. /s"mandrel flex test Passed. Pencil hardness B. Solvents, 15 min;

Toluene Unchanged. Methyl isobutylketone Unchanged. Cold Water, 24 hoursUnchanged. 5% aqueous NaOH, 60 min Unchanged.

EXAMPLE II 100 parts of Polyether A was combined with 60 parts of1,3,S-tris(beta-mercaptoethyl) 2,4,6-trioxane and 2 parts ofbenzylmethylamine and the mixture was used as an adhesive for etchedaluminum. The mixture was applied between two pieces of aluminum and theassembly cured at room temperature and at 100 C. The strengths of thebonds are indicated below:

P.s.i. tensile shear Cured 2 hrs., 100 C. 5604 Cured 3 days at roomtemp. 1372 EXAMPLE III The adhesive shown in Example II was used to bondconcrete to concrete. The strengths are shown below:

P.s.i.

Cured 48 hours, room temp. (no catalyst) 528 Cured 48 hours, room temp.540 Cured 48 hours, room temp. and soaked in water one week 422 Allbreaks were concrete failures rather than bond failures.

EXAMPLE IV About 100 parts of Polyether A was combined with 60 parts of2,4,6-tris(beta-mercaptoethyl) 1,3,5-trioxane and 2 parts of trisdimethylaminomethyl) phenol and the mixture spread out as a coating(about 3.0 mils thick) on EXAMPLE V About 100 parts of Polyether B, 38parts of 2,4,6- tris(beta-mercaptoethyl) 1,3,5-trioxane, 2 parts of tris(dimethylaminomethyl)phenol and 43 parts of 50/50 mixture of toluene andmethyl ethyl ketone were mixed together with stirring. The resultingcomposition was spread out as a coating (about 25 mils thick) on tinpanels. The coating was allowed to cure in air at 25 C.

11. A process for curing a glycidyl ether of bis(hydroxyphenyl) propanewhich comprises reacting the compound With a tris(mercaptoalkyl)trioxane in the presence of .01 to 5% by weight of a tertiary amine.

12. A composition comprising a mixture of a polyepoxide having more thanone vie-epoxy group and a heterocyclic compound substituted in from 3 to5 difierent places on the heterocyclic ring with a SH group or -RSHgroup wherein R is an aliphatic hydrocarbon radical containing from 1 to6 carbon atoms, the heteroatom in the heterocyclic ring being a memberof the group consisting of oxygen, sulfur and nitrogen.

13. A composition comprising a mixture of a polyepoxide having more thanone Vic-epoxy group and a poly (mercaptoalkyl) trioxane wherein thereare from 3 to 5 mercaptoalkyl groups on the trioxane molecule.

14. A composition obtained by reacting a polyepoxide having more thanone Vic-epoxy group with heterocyclic compound substituted in from 3 to5 different places on the heterocyclic ring with a SH or RSH groupwherein R is an aliphatic hydrocarbon radical containing from 1 to 6carbon atoms, the heteroatom in the heterocyclic ring being a member ofthe group consisting of oxygen, sulfur and nitrogen, and a tertiaryamine activator.

References Cited by the Examiner UNITED STATES PATENTS 2,915,485 12/1959Shokal 26047 SAMUEL H. BLECH, Primary Examiner.

T. D. KERWIN, Assistant Examiner.

1. A PROCESS FOR CURING AND RESINIFYING A POLYEPOXIDE HAVING MORE THANONE VIC-EPOXY GROUP WHICH COMPRISES MIXING AND REACTING THE POLYEPOXIDEWITH A HETEROCYCLIC COMPOUND SUBSTITUTED IN FROM 3 TO 5 DIFFERENT PLACESON THE HETEROCYCLIC RING WITH A-SH RADICAL OR A-RSH RADICAL WHEREIN R ISAN ALIPHATIC HYDROCARBON RADICAL CONTAINING FROM 1 TO 6 CARBON ATS, THEHETEROATOM IN THE HETEROCYCLIC RING BEING A MEMBER OF THE GROUPCONSISTING OF OXYGEN, SULFUR AND NITROGEN.